Sunday, January 15, 2012

(Update: The stone pit operator, Futaba Saiseki Kogyo, sold the crushed stones to the concrete company in Nihonmatsu City in Fukushima which has since closed down. There is no record kept at the concrete company of where the concrete was sold and how much. The stone pit operator sold about 1000 tonnes to the concrete company, and the remaining 4000 tonnes or so to 20 construction companies inside Fukushima Prefecture.

The stone pit operator executive says he didn't know much about radiation, and that he would have stopped selling if the government had told him to. Information in Japanese, here and here.)

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For now, the media has decided to focus on the aggregate in the concrete used in the foundation of the apartment in Nihonmatsu City, Fukushima. The crushed stones from a stone pit in Namie-machi in the planned evacuation zone just outside the no-entry zone were freely shipped and sold until April 22, and several hundred job sites in Fukushima Prefecture may have used the stones.

The concrete contaminated with radioactive materials from the Fukushima I Nuclear Power Plant accident was used in the construction of an apartment in Nihonmatsu City in Fukushima Prefecture. The radiation from the floor of the 1st floor of the apartment was higher than that of outside. The city and the national government announced on January 15, 2012.

The high radiation is thought to be coming from the stones used in the concrete mix; the stones came from a stone pit inside the planned evacuation zone. The same stones have been used in several hundred job sites, and the national government is investigating the distribution routes of the stones and the concrete.

According to the announcement, the contaminated concrete was used in the foundation of the 3-story apartment made of ferro-concrete in Wakamiya District of Nihonmatsu City. The apartment was finished construction in July last year. At 1 meter off the floor in a room on the 1st floor, the radiation level is 1.16 to 1.24 microsievert/hour. The radiation level outside is 0.7 to 1.0 microsievert/hour. On the 2nd and 3rd floors, the radiation level inside rooms is 0.1 to 0.38 microsievert/hour.

The crushed stones used in the concrete were transported from a stone pit in Minami Tsushima in Namie-machi, inside the planned evacuation zone. 57.5 cubic meters of concrete was used in the foundation of the apartment building on April 11 last year.

At the stone pit, they crushed the stones that had been picked before the nuclear accident, and the crushed stones were kept outdoors and continued to be sold until the area was designated as evacuation zone on April 22. According to the Ministry of Economy, Trade and Industry, the stone pit operator sold 5200 tonnes of stones to 19 companies in Fukushima Prefecture. The concrete company in Nihonmatsu City who delivered concrete to the apartment site has sold concrete to over 100 companies in Fukushima Prefecture, and the concrete was used at several hundred job sites.

Nihonmatsu City measured the cumulative external radiation exposure of children from September through November last year. A female junior high school student who lives in the apartment was found with 1.62 millisievert cumulative radiation for the 3 months, and the city conducted the investigation. There are 12 families living in the apartment.

マンション１階の室内に２４時間滞在する仮定で計算すると、年間の線量は１０ミリシーベルト前後になる。

If you stay inside a room on the 1st floor of the apartment for 24 hours, the cumulative radiation in one year would be about 10 millisieverts.

NHK runs a similar story, quoting the Ministry of Economy saying it must be the crushed stones from that particular stone pit in Namie-machi. That's the official story.

It's a bit hard to believe hard crushed stones has that much radiation on the surface considering the surface-to-volume ratio. On the other hand, small particles like ashes may. But the official story is set, and the net citizens on blogs and Twitter are left wondering "What about cement? What about additives in concrete? What about steel mesh or rebar?"

It is also convenient to blame everything on one stone pit operator than to have to check every bag of cement from the cement companies.

Another thing that strikes me as odd is the amount of crushed stones sold from this stone pit operator in such a short period of time between the March 11 accident and April 22. I suspect the situation may be similar to the cattle farmers in the planned evacuation zone who managed to sell their cows which were later found with high levels of radioactive cesium, before any rigorous testing started.

Hmmm. This is starting to feel like the radioactive beef and radioactive rice debacles from last year where first denying the problem and then insisting the problem was an exception, and doing perfunctory sample testing totally backfired on the government. We'll see if this story goes quiet very quickly.

"Could the radioactivity come from the cement? They use rice hulls in cement making now---actually, they use it in a lot of things."

Actually they use many different things as fillers in cement mortar and concrete.For example, in pre-mixed mortar it is allowable to mix in two percent wastes in Germany. Sewer sludges, fly ashes, toxic chemical waste - it's all permitted and used. The producers of the waste pay the concrete manufacturers to take their waste, both profit.The only way to avoid this risk is the use of pure cement (in which such "additives" aren't allowed) and mix it on the job site with (hopefully clean) sand and stones.

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I am Japanese, and I not only read Japanese news sources for information on earthquake and the Fukushima Nuke Plant but also watch press conferences via the Internet when I can and summarize my findings, adding my observations.

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